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Intra-articular injections are injections that are given into a joint, such as the elbow or the knee. The prefix “intra” means inside or within and “articular” is the medical term that refers to a joint space. Injections to the intra-articular space are commonly used to reduce inflammation that may be caused by conditions such as osteoarthritis, synovitis, or bursitis.
Intra-articular injections offer several advantages over regular intramuscular, or into-the-muscle, injections. If the medication being injected is to treat local inflammation in the joint, intra-articular injection places the medication directly at the sight of need. The medication can take effect much more quickly than if the chemicals must be systemically absorbed following an intramuscular injection. Also, because there is no systemic absorption, systemic side effects of medications can be avoided.
Another advantage of intra-articular injections is that they allow for direct interaction with the joint fluid. A joint, where two bones meet, is surrounded by the joint capsule that contains a lubricating fluid. This fluid, known as synovial fluid, facilitates the movement of the bones over one another. In conditions such as arthritis, the viscoelasticity, or springiness, of the joint fluid can decrease. Intra-articular injections of hyaluronic acid can increase the viscoelasticity in a process known as viscosupplementation.
Arthritis is probably the best known condition that is commonly treated with intra-articular injections. Cases of osteoarthritis, post-traumatic osteoarthritis, gouty arthritis, and rheumatoid arthritis are all candidates for the injections. Other conditions that are commonly treated with intra-articular injections include synovitis, bursitis, carpal tunnel syndrome, ganglion cysts, and neuromas. Depending on the condition being treated, multiple injections may be necessary. The most successful intra-articular treatment is used in combination with other therapies, such as non-steroidal anti-inflammatory systemic medications, stretching or physical therapy, and alternating heat and ice therapy.
Several common medications are used intra-articularly. Various corticosteroids are used to decrease inflammation and pain within the joint space. Hyaluronic acid is used to increase viscoelasticity. Additionally, analgesic medications are being tested for intra-articular use to reduce intra- and post-operative pain for orthopedic surgeries.
Common sites for intra-articular injection include the knee, elbow, and shoulder. Sterile preparation of the injection site with alcohol, betadine, and sterile gloves is often used to reduce the risk of injecting bacteria into the normally sterile joint space. Ultrasound or fluoroscopy is often used to guide injections into hard-to-access joints, such as the hip, although medical studies have shown that ultrasound guidance improves accuracy for all intra-articular injections.